1. Field of the Invention
The present invention relates generally to DownLink (DL) communication in a multi-cellular wireless communication system.
2. Description of the Related Art
Future-generation mobile communication and wireless communication systems require higher data rates and an increased system capacity in a multi-cellular environment having a plurality of sub-cells that share a control channel. As a result, research has been conducted on different Multiple Input Multiple Output (MIMO) systems that transmit data through a plurality of antennas.
Among the MIMO systems, a closed-loop MIMO system increases a data rate and transmission performance using channel state information in the multi-cellular environment having a plurality of sub-cells that share a control channel. In the closed-loop MIMO system, a Base Station (BS) receives, as feedback information, UpLink (UL) control information about a DL transmission channel from a User Equipment (UE) that the BS is to service. For example, the feedback information about the DL transmission channel includes a Channel Quality Indicator (CQI), a Precoding Matrix Index (PMI), etc. Thereafter, the BS transmits data to the UE based on the UL control information.
Although the closed-loop MIMO system is being studied and used for a multi-cellular environment and a single-cellular environment, studies and developments are needed for a technique that mitigates interference from other cells, when the closed-loop MIMO system is used in a multi-cellular environment.
In the multi-cellular environment, the same cell IDentifier (ID) is assigned to each sub-cell, irrespective of the number of transmission antennas. If cells are densely populated, due to an increase of an amount of data, inter-cell interference increases and network geometry gets complicated. Further, the overhead of inter-cell handover reduces performance.